Wheel and tire assembly including a collapsible wheel

ABSTRACT

A wheel assembly includes a collapsible wheel and an airless flexible tire mounted on the wheel. The wheel includes a central portion and a plurality of circumferentially spaced mounting elements attached to the central portion. Each of the mounting elements is movable between a retracted position and an extended position, and may be pivotally attached to the central portion of the wheel and configured to pivot between the retracted position and the extended position. The tire may be positioned on the wheel when one or more of the mounting elements is in the retracted position, and the one or more mounting elements are moved to the extended position wherein the mounting elements engage and support the tire.

RELATED APPLICATIONS

The present application is a divisional application of co-pending U.S.Patent Application titled WHEEL AND TIRE ASSEMBLY INCLUDING ACOLLAPSIBLE WHEEL, Ser. No. 13/969,197, filed Aug. 16, 2013. Theidentified earlier-filed application is hereby incorporated by referencein its entirety into the present application.

FIELD

Embodiments of the present invention relate to wheel and tireassemblies. More particularly, embodiments of the present inventionrelate to wheel and tire assemblies including collapsible wheels andairless tires presenting certain performance characteristics ofpneumatic tires.

BACKGROUND

One type of irrigation system includes elevated water conduits supportedby mobile towers. Such mobile towers are mounted on wheels that propelthe towers along the ground to be irrigated. The wheels typicallyinclude pneumatic tires that require periodic maintenance, includingadjusting air pressure, repairing tires that develop holes or otherdamage, and replacing old or damaged tires that are beyond repair.

Because irrigation systems are typically used in fields or other remotelocations, monitoring the tires for problems and reaching the tires toperform maintenance and repairs can be inconvenient or difficult. If atire loses air pressure and is not repaired in a timely manner, damageto the tire, to the equipment mounted on the tire, or both may result.

One solution to the challenges presented by the use of pneumatic tiresinvolves using wheels without tires. While this approach addresses mostof the problems of tire maintenance, repair and replacement, it presentsother challenges. Tireless wheels, for example, are rigid and experiencegreater ground penetration than a flexible tire, thereby creating rutsor otherwise disturbing the land more than a pneumatic tire. Similarproblems exist for tractors, automobiles, and other vehicles thattypically use pneumatic tires.

The above section provides background information related to the presentdisclosure which is not necessarily prior art.

SUMMARY

A wheel assembly constructed in accordance with an embodiment of thepresent invention comprises a wheel and an airless flexible tire mountedon the wheel. The wheel includes a central portion and a plurality ofcircumferentially spaced mounting elements attached to the centralportion. Each of the mounting elements is movable between a retractedposition and an extended position and support the tire when in theextended position.

An irrigation system constructed in accordance with another embodimentof the invention comprises a conduit for carrying and dispensing water,at least one mobile tower for supporting and moving the conduit, and aplurality of wheel assemblies for supporting the at least one mobiletower. Each of the wheel assemblies includes a wheel with a centralportion and a plurality of circumferentially spaced mounting elementsattached to the central portion, and each of the mounting elements ismovable between a retracted position and an extended position. Anairless flexible tire is mounted on the wheel and is supported by themounting elements when the mounting elements are in the extendedposition.

A method of mounting an airless tire on a wheel in accordance with yetanother embodiment of the invention comprises moving a plurality ofmounting elements on the wheel from an extended position to a retractedposition, positioning the wheel and the tire such that the wheel isinside the tire, and moving the plurality of mounting elements from theretracted position to the extended position such that the mountingelements engage the tire.

This summary is provided to introduce a selection of concepts in asimplified form that are further described in the detailed descriptionbelow. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the present invention will be apparent from thefollowing detailed description of the embodiments and the accompanyingdrawing figures.

DRAWINGS

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a perspective view of an exemplary irrigation system includingwheel assemblies constructed in accordance with embodiments of theinvention.

FIG. 2 is a front side perspective view of one of the wheel assembliesof FIG. 1, the wheel assembly including a collapsible wheel and aflexible airless tire mounted on the wheel.

FIG. 3 is a rear side perspective view of the wheel assembly of FIG. 2.

FIG. 4 is an exploded view of the wheel assembly of FIG. 2.

FIG. 5 is a side elevation view of the wheel assembly of FIG. 2,illustrating a plurality of mounting elements in a retracted position.

FIG. 6 is a side elevation view of the wheel assembly of FIG. 2,illustrating the plurality of mounting elements in an extended positionand engaging the tire.

FIG. 7 is a fragmentary view of the wheel assembly of FIG. 2,illustrating the mounting elements in the retracted position.

FIG. 8 is a fragmentary view of the wheel assembly of FIG. 2,illustrating the mounting elements in the extended position.

FIG. 9 is a fragmentary, cross-sectional view of the wheel assembly ofFIG. 2.

FIG. 10 is an environmental side elevation view of the wheel assembly ofFIG. 2 illustrating the wheel assembly mounted on the irrigation systemof FIG. 1 and engaging the ground.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description of embodiments of the inventionreferences the accompanying drawings. The embodiments are intended todescribe aspects of the invention in sufficient detail to enable thoseskilled in the art to practice the invention. Other embodiments can beutilized and changes can be made without departing from the scope of theclaims. The following detailed description is, therefore, not to betaken in a limiting sense. The scope of the present invention is definedonly by the appended claims, along with the full scope of equivalents towhich such claims are entitled.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment”, “an embodiment”, or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the present technology can include a variety of combinationsand/or integrations of the embodiments described herein.

Turning now to the drawing figures, and initially FIG. 1, an irrigationsystem 10 constructed in accordance with embodiments of the invention isillustrated and includes a plurality of wheel assemblies. Theillustrated irrigation system 10 is a central pivot irrigation systemthat broadly comprises a fixed central pivot 12 and a main section 14pivotally connected to the central pivot 12. The irrigation system 10may also comprise an extension arm (also commonly referred to as a“swing arm” or “corner arm”) pivotally connected to the free end of themain section 14.

The fixed central pivot 12 may be a tower or any other support structureabout which the main section 14 may pivot. The central pivot 12 hasaccess to a well, water tank, or other source of water and may also becoupled with a tank or other source of agricultural products to injectfertilizers, pesticides and/or other chemicals into the water forapplication during irrigation.

The main section 14 may comprise a number of mobile support towers16A-D, the outermost 16D of which is referred to herein as an “endtower”. The support towers are connected to the fixed central pivot 12and to one another by truss sections 18A-D or other supports to form anumber of interconnected spans. The irrigation system 10 illustrated inFIG. 1 includes four mobile support towers 16A-D; however, it maycomprise any number of mobile support towers without departing from thescope of the present invention.

Each mobile tower may include a drive tube 20A-D on which a pair ofwheel assemblies 22A-D is mounted. Embodiments of the wheel assemblies22A-D are described in more detail below. A drive motor 24A-D is mountedto each drive tube 20A-D for driving the wheel assemblies 22A-D. Themotors 24A-D may include integral or external relays so they may beturned on, off, and reversed. The motors may also have several speeds orbe equipped with variable speed drives.

Each of the truss sections 18A-D carries or otherwise supports a conduitsection 26A-D or other fluid distribution mechanism that is connected influid communication with all other conduit sections. A plurality ofsprinkler heads, spray guns, drop nozzles, or other fluid-emittingdevices are spaced along the conduit sections 26A-D to apply waterand/or other fluids to land underneath the irrigation system.

The irrigation system 10 may also include an optional extension arm (notshown) pivotally connected to the end tower 16D and supported by a swingtower with steerable wheels driven by a motor. The extension arm may bejoined to the end tower by an articulating pivot joint. The extensionarm is folded inward relative to the end tower when it is not irrigatinga corner of a field and may be pivoted outwardly away from the end towerwhile irrigating the corners of a field.

The irrigation system 10 may also include one or more high pressuresprayers or end guns 28 mounted to the end tower 16D or to the end ofthe extension arm. The end guns 28 may be activated at the corners of afield or other designated areas to increase the amount of land that canbe irrigated.

It will be appreciated that the irrigation system 10 is illustrated anddescribed herein as one exemplary implementation of the wheel assemblies22 described in detail below. Other, equally preferred implementationsof the wheel assemblies 22 not shown or discussed in detail herein mayinclude, without limitation, other types of irrigation systems, such aslateral irrigation systems, other types of agricultural equipment, suchas wagons, carts, implements, and so forth, or other types of vehiclessuch as buses, trucks, and automobiles. However, embodiments of theinvention are especially suited for irrigation systems and othervehicles or systems that travel over unpaved or unfinished ground.

Referring now to FIGS. 2-10, a wheel assembly 22 constructed inaccordance with embodiments of the invention is illustrated. The wheelassembly 22 broadly includes a wheel 30 and a flexible airless tire 32mounted on the wheel 30 in a generally circumscribing relationship tothe wheel 30. The wheel 30 is collapsible to facilitate mounting thetire on and removing the tire from the wheel 30, as explained below. Asused herein, a wheel is “collapsible” if one or more of the portions ofthe wheel that engage the tire may be moved radially inwardly to therebyrelieve tension on and/or disengage the tire.

The wheel 30 and the tire 32 are also configured such that the tire 32,while being airless, has some characteristics of a pneumatic tire thatimprove the performance of the tire. For example, the wheel 30 and tire32 are configured such that portions of the tire 32 flex radiallyinwardly toward the wheel 30 in response to ground engaging pressure, asillustrated in FIG. 10. It will be appreciated that this flexing actionincreases the total ground engaging footprint of the wheel assembly 22,thus distributing the weight of the wheel assembly 22 and the weight ofany machinery supported by the wheel assembly 22 over a larger area andlimiting the total amount of ground penetration of the wheel assembly22. Additionally, ground penetration of traction lugs or otherground-gripping elements of the tire 32 is limited, as explained belowin greater detail.

As used herein, “ground engaging pressure” refers to pressure exerted onthe wheel assembly 22 by the ground when the wheel assembly 22 is atrest on the ground or rolling on the ground. Ground engaging pressuremay include pressure exerted on the wheel assembly 22 from differentdirections or from multiple directions simultaneously, such as where thewheel assembly 22 is on inclined terrain or rolling over an obstacle.Ground engaging pressure is related to the weight of the wheel assembly22 and to the weight of any machinery supported by the wheel assembly22, and thus will vary from one embodiment of the invention to anotherand from one implementation to another.

The wheel 30 is configured to engage the tire 32 at circumferentiallyspaced locations such that portions of the tire 32 between the points ofengagement flex radially inwardly in response to ground engagingpressure. In the illustrated embodiment, the wheel 30 includes a discshaped inner portion 34 and a plurality of circumferentially spacedmounting elements 36 movably attached to a radially outer margin 38 ofthe inner portion 34. The inner portion 34 of the wheel 30 includes aninnermost hub 40 with a plurality of apertures for attaching to, forexample, lug nuts or similar attachment components.

Each of the mounting elements 36 is movable between a retracted position(FIGS. 5 and 7) and an extended position (FIGS. 6 and 8). Each of themounting elements 36 presents an elongated, transversely orientedradially outer edge 42. When the mounting elements 36 are in theextended position, the outer edges 42 are distal the inner portion 34and engage the tire 32 to thereby support the tire 32 relative to thewheel 30. When the mounting elements 36 are in the retracted position,the outer edges 42 are proximate the inner portion 34. As illustrated,the length of the outer edge 42 is approximately the same as the widthof the tire 32. Furthermore, the outer edge 42 defines a gap 44configured to engage a portion of the tire 32 to prevent the tire 32from shifting laterally relative to the wheel 30, as explained below.

In the illustrated embodiment, each of the mounting elements 36 presentsa Y-shape with a lower portion 46 configured to attach to the outermargin 38 of the wheel 30 and a widening upper portion 48 including theouter edge 42 configured to engage the tire 32. A slot 50 in the lowerportion 46 enables the mounting element 36 to slidingly engage the outermargin 38 of the wheel 30, and a pair of through-holes 52 in the lowerportion 46 of each mounting element 36 align with a corresponding pairof apertures 54 in the outer margin 38 of the wheel 30. Bolts 56 orsimilar connectors are inserted through the through-holes and theapertures 52 to secure the mounting elements 36 to the inner portion 34of the wheel 30. As illustrated in FIGS. 5 and 6, by removing aninnermost one of the bolts 56, the mounting elements 36 are permitted topivot about the other one of the bolts 56, wherein the mounting element36 is movable between the retracted position (FIG. 5) and the extendedposition (FIG. 6).

Each mounting element 36 may be constructed of a single, unitary pieceof material, such as metal, that is folded, cast or otherwise formed tothe desired shape and configuration. Furthermore, all of the mountingelements 36 may be identical in size and shape. By way of example, eachof the mounting elements 36 may be constructed by cutting a piece ofmetal to a particular flat shape and then forming the piece of metal tothe desired shape through a series of bending and forming steps.Alternatively, each of the mounting elements may comprise two or moreparts assembled to form a single structure.

The mounting elements 36 are approximately equally spaced around theinner portion 34 of the wheel 30 and extend radially outwardly from theinner portion 34. When the tire 32 is mounted on the wheel 30 and themounting elements 36 are in the extended position, the mounting elements36 engage portions of the tire 32 such that the tire 32 is separatedradially from the inner portion 34 of the wheel 30 by a space. Thisconfiguration allows portions of the tire 32 to flex inwardly toward thecentral portion 34 in response to ground engaging pressure, as explainedabove. As used herein, the mounting elements 36 extend radiallyoutwardly from the inner portion 34 if at least a portion of each of themounting elements 36 is positioned radially outwardly of the innerportion 34 of the wheel 30.

In the illustrated embodiment, the wheel assembly 22 includes tenmounting elements 36 approximately equally spaced around the outermargin 38 of the wheel 30. If the wheel 30 includes ten mountingelements 36 (as illustrated), the angular separation of the mountingelements 36 is approximately thirty-six degrees. Thus, if the wheel 30is about forty-eight inches in diameter at the edges 42, the outer edges42 of the mounting elements 36 are spaced approximately twelve andone-half inches apart. If the wheel 30 is about fifty inches in diameterat the outer edges 42, the mounting elements 36 are spaced approximatelythirteen inches apart at the outer edges 42. If the wheel 30 is abouttwenty-four inches in diameter at the outer edges 42, the mountingelement 36 pairs are spaced approximately six inches apart at the outeredges 42.

The tire 32 is configured to be mounted on the wheel 30 such that atleast a portion of the tire 32 engages the mounting elements 36 and thetire 32 presents a generally circular or nearly circular outer profile.Advantageously, the wheel 30 is configured for use with an airless tire.As used herein, a “tire” is a flexible component positioned andconfigured to engage the ground during use of the wheel assembly 22. An“airless tire” is a tire that does not require trapped or compressed airfor normal and proper use. An airless tire may be constructed of asingle, unitary piece of material or multiple pieces of material. Asexplained above and illustrated in FIG. 10, the tire 32 is configured toflex inwardly in response to ground engaging pressure. As used herein,the tire 32 can “flex” if it can deflect or bend repeatedly and returnto its original shape.

The illustrated tire 32 includes a body 58 that is generally cylindricalin shape with a plurality of traction lugs 60 extending radiallyoutwardly from an outer side of the body 58 and a plurality of drivelugs 62 extending radially inwardly from an inner side of the body 58.In the illustrated embodiment, the outer side 64 of the tire body 58 isgenerally transversely flat, that is, the outer side of the bodypresents little or no curvature from a first edge to a second edge ofthe tire. Similarly, the inner side 66 of the tire body 58 is alsogenerally transversely flat.

The traction lugs 60 engage the ground and help prevent the wheelassembly 22 from slipping relative to the ground. The illustratedfraction lugs 60 are generally rectangular or trapezoidal in shape andtransversely oriented on the tire 32, are integrally formed with thetire 32 and may be approximately equally spaced circumferentially aroundthe outer side 64 of the tire body 58. As illustrated in FIG. 6, thetire 32 may be configured such that the traction lugs 60 are positionedintermediate the mounting elements 36. This configuration allows theportion of the tire 32 bearing the traction lug 60 to flex inwardly inresponse to ground engaging pressure. This performance characteristicallows each traction lug 60 to engage the ground, yet limits the amountof ground penetration and soil disturbance. It may be desirable in someimplementations to position the traction lugs 60 proximate or in directradial alignment with the mounting elements 36. Such alternativeconfigurations of the tire 32 are within the ambit of the presentinvention.

As illustrated in FIG. 6, certain traction lugs 60 b may be larger(i.e., have a greater radial reach) than other traction lugs 60 a. Inthe illustrated embodiment, one of every three traction lugs has agreater radial reach, corresponding to a position that is approximatelyhalf the distance between consecutive mounting elements 36. Thus, thereare three traction lugs between consecutive mounting elements 36, withthe middle traction lug being the largest.

The drive lugs 62 engage the wheel 30 and prevent the tire 32 fromshifting longitudinally or laterally on the wheel 30. In the illustratedembodiment, the drive lugs 62 are arranged in pairs corresponding to themounting elements 36 such that the drive lugs 62 are adjacent themounting elements 36 on opposite sides of the mounting elements 36. Eachof the drive lugs 62 is integrally formed in the tire 32 and presents agenerally elongated body with a cross member 68 connecting each drivelug 62 pair. Each of the cross members 68 is located at a center of thetire 32 and corresponds to the gap 44 defined by the outer edge 42 ofthe mounting elements 36.

The tire 32 is constructed of a flexible material, such as rubber, PVCor plastic. The tire 32 may be configured such that as the tire flexesinwardly toward the wheel 30, the flexed portion of the tire 32 remainstransversely flat or substantially transversely flat. This may bedesirable, for example, to preserve a wide footprint or otherwise limitthe amount of ground penetration. With particular reference to FIGS.7-9, one or more tension elements 70 may be secured to the tire 32 togive the tire 32 added structural strength and resilience. As usedherein, a tension element 70 is “secured to” the tire 32 if it ispartially or completely embedded in the tire 32 or otherwise attached orconnected to the tire 32. A first tension element 70 a may be placed ina first axial side of the tire body 58 and a second tension element 70 bmay be placed in a second axial side of the tire body 58. Alternatively,a single tension element may be located in a central portion of the tire32. The tension elements 70 are preferably completely embedded in thetire 32, as illustrated.

The tension elements 70 are preferably more resilient than the materialused to construct the tire 32 such that the one or more tension elements70 increase the overall resilience of the tire 32, strengthening thestructure of the tire 32 and enabling the tire 32 to return to itsoriginal shape after being subject to deflection during use. The one ormore tension elements 70 may be constructed of metal, such as springsteal, or other resilient and durable material. More particularly, eachof the tension elements 70 may be a metal band constructed of a solidpiece of metal or of multiple bonded or braided metal elements. Thetension elements 70 may present a width that is between 0.05 and 0.5times a total width of the tire, such as 0.1, 0.2 or 0.3 times the totalwidth of the tire. If the tire 32 is twelve inches wide, for example,each of the tension elements 70 may be about two or two and one-halfinches wide and between one-eighth and one-half of an inch thick.

The wheel 30 is constructed of a rigid material such as, for example,metal, plastic or a composite material. The size of the wheel assembly22 may vary substantially from one embodiment of the invention toanother without departing from the scope of the invention. It will beunderstood that the dimensions and ranges set forth herein areexemplary, and not limiting, in nature. The diameter of the wheel 30 ispreferably within the range of from about twenty-four inches to aboutsixty inches and more preferably within the range of from aboutthirty-six inches to about forty-eight inches. The width of the wheel 30(i.e., the total width of each of the mounting elements 36) ispreferably within the range of from about six inches to about eighteeninches and more preferably within the range of from about eight inchesto about sixteen inches. The diameter of the inner portion 34 of thewheel 30 is preferably between about 0.6 and 0.9 times the totaldiameter and may particularly be about 0.8 times the total diameter.

The thickness of the tire body 58 is preferably within the range of fromabout one-half inch to about three inches, more preferably within therange of from about one inch to about two inches. The height of thetraction lugs 60 is preferably within the range of from aboutone-quarter inch to about four inches, more preferably within the rangeof from about one-half inch to about three inches. In one exemplaryembodiment, the wheel assembly 22 is about eleven inches wide and aboutfifty-two inches in diameter. The tire body preferably presents a widthto thickness ratio of between five and twenty.

The collapsible configuration of the wheel facilitates mounting the tire32 on the wheel 30 an removing the tire 32 from the wheel 30. To mountthe tire 32 on the wheel 30, for example, one or more of the mountingelements 36 are placed in the retracted position to facilitate placementof the tire 32 on the wheel 30. In the illustrated embodiment, themounting elements 36 are placed in the retracted position by removingone of the bolts 56 and allowing the mounting elements 36 to pivot aboutthe remaining bolt 56. It may be desirable to place all or most of themounting elements 36 in the retracted position, but it will beappreciated that in some circumstances placing as few as one of themounting elements 36 in the retracted position is sufficient toaccommodate placement of the tire 32 on the wheel 30.

When the tire 32 is placed on the wheel 30, the mounting elements 36 aremoved from the retracted position (FIGS. 5 and 7) to the extendedposition (FIGS. 6 and 8), thereby causing the mounting elements 36 tofirmly engage the tire 32 and secure the tire 32 on the wheel 30.

Although the invention has been described with reference to thepreferred embodiment illustrated in the attached drawing figures, it isnoted that equivalents may be employed and substitutions made hereinwithout departing from the scope of the invention as recited in theclaims. By way of example, the particular configuration of the mountingelements 36 that enables movement between the retracted and the extendedpositions may vary from one embodiment of the invention to anotherwithout departing from the spirit or scope of the invention. In additionto the pivoting configuration illustrated and described herein, themounting elements 36 may be configured to slide or otherwise movebetween the extended and retracted positions.

Having thus described the preferred embodiment of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A method of mounting an airless tire on a wheel havinga plurality of mounting elements, the method comprising: moving at leastsome of the mounting elements on the wheel from an extended position toa retracted position; positioning the wheel and the tire such that thewheel is inside the tire; and moving the at least some of the mountingelements from the retracted position to the extended position such thatthe plurality of mounting elements engage the tire.
 2. The method as setforth in claim 1, the steps of moving at least some of the plurality ofmounting elements from the extended position to the retracted positionand moving at least some of the mounting elements from the retractedposition to the extended position including moving all of the mountingelements.
 3. The method as set forth in claim 1, the steps of moving atleast some of the plurality of mounting elements from the extendedposition to the retracted position and moving at least some of themounting elements from the retracted position to the extended positionincluding moving only one of the mounting elements.
 4. The method as setforth in claim 1, the steps of moving at least some of the plurality ofmounting elements from the extended position to the retracted positionand moving at least some of the mounting elements from the retractedposition to the extended position including pivoting the at least someof the mounting elements.
 5. The method as set forth in claim 1, whereineach mounting element to be moved is connected to the wheel via at leastone fastener, the method further comprising the steps of removing the atleast one fastener from each mounting element to be moved so that themounting elements can be moved from the extended position to theretracted position and connecting the moved mounting elements to thewheel via the fasteners so as to retain the mounting elements in theextended position.
 6. The method as set forth in claim 5, wherein the atleast one fastener includes first and second fasteners and each mountingelement is configured to be pivoted about the second fastener.
 7. Themethod as set forth in claim 6, wherein the first and second fastenersare nuts and bolts, and the method further comprises the step ofloosening the first fastener so that the mounting element can pivotabout the second fastener.
 8. The method as set forth in claim 1, thestep of moving at least some of the mounting elements on the wheel fromthe extended position to the retracted position including pivoting theat least some of the mounting elements in a first direction and the stepof moving the at least some of the mounting elements on the wheel fromthe retracted position to the extended position including pivoting theat least some of the mounting elements in a second direction oppositethe first direction.
 9. The method as set forth in claim 1, the step ofmoving the at least some of the mounting elements from the refractedposition to the extended position including urging distal ends of themounting elements into drive lugs positioned on an inner side of thetire.
 10. The method as set forth in claim 9, wherein the drive lugs ofthe tire each include an annularly extending cross member and the distalends of the mounting elements each include a recess configured toreceive the cross member therein for preventing the tire from shiftinglaterally relative to the wheel.
 11. A method of mounting an airlesstire on a wheel of a mobile tower of an irrigation system, the wheelhaving a plurality of mounting elements, the method comprising: movingat least some of the mounting elements on the wheel from an extendedposition to a retracted position; positioning the wheel and the tiresuch that the wheel is inside the tire; and moving the at least some ofthe mounting elements from the retracted position to the extendedposition such that the plurality of mounting elements engage the tire.12. The method as set forth in claim 11, the steps of moving at leastsome of the plurality of mounting elements from the extended position tothe retracted position and moving at least some of the mounting elementsfrom the retracted position to the extended position including movingall of the mounting elements.
 13. The method as set forth in claim 11,the steps of moving at least some of the plurality of mounting elementsfrom the extended position to the retracted position and moving at leastsome of the mounting elements from the retracted position to theextended position including moving only one of the mounting elements.14. The method as set forth in claim 11, the steps of moving at leastsome of the plurality of mounting elements from the extended position tothe retracted position and moving at least some of the mounting elementsfrom the retracted position to the extended position including pivotingthe at least some of the mounting elements.
 15. The method as set forthin claim 11, wherein each mounting element to be moved is connected tothe wheel via at least one fastener, the method further comprising thesteps of removing the at least one fastener from each mounting elementto be moved so that the mounting elements can be moved from the extendedposition to the retracted position and connecting the moved mountingelements to the wheel via the fasteners so as to retain the mountingelements in the extended position.
 16. The method as set forth in claim15, wherein the at least one fastener includes first and secondfasteners and each mounting element is configured to be pivoted aboutthe second fastener.
 17. The method as set forth in claim 11, the stepof moving at least some of the mounting elements on the wheel from theextended position to the retracted position including pivoting the atleast some of the mounting elements in a first direction and the step ofmoving the at least some of the mounting elements on the wheel from theretracted position to the extended position including pivoting the atleast some of the mounting elements in a second direction opposite thefirst direction.
 18. The method as set forth in claim 11, the step ofmoving the at least some of the mounting elements from the refractedposition to the extended position including urging distal ends of themounting elements into drive lugs positioned on an inner side of thetire.
 19. The method as set forth in claim 18, wherein the drive lugs ofthe tire each include an annularly extending cross member and the distalends of the mounting elements each include a recess configured toreceive the cross member therein for preventing the tire from shiftinglaterally relative to the wheel.
 20. A method of mounting an airlesstire on a wheel of a mobile tower of an irrigation system, the wheelhaving a plurality of mounting elements, the method comprising: removinga first fastener connecting each mounting element to the wheel;loosening a second fastener connecting each mounting element to thewheel; pivoting at least some of the mounting elements on the wheelabout the second fastener in a first direction from an extended positionto a retracted position; positioning the wheel and the tire such thatthe wheel is inside the tire; pivoting the at least some of the mountingelements about the second fastener in a second direction from theretracted position to the extended position; inserting distal ends ofthe at least some of the mounting elements into engagement with drivelugs of the tire; inserting annularly extending cross members of thedrive lugs into recesses positioned on distal ends of the mountingelements for preventing the tire from shifting laterally relative to thewheel; tightening the second fastener connecting each mounting elementto the wheel; engaging the first fastener between each mounting elementand the wheel; and tightening the first fastener so that the mountingelements are coupled to the wheel and firmly engage the tire such thatthe tire is secured on the wheel.